Additional Financial Statement Information - Additional Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, Net
Commodity Sales	$ 383	$ 455
Joint Interest Billings	137	207
Other	111	103
Allowance for Doubtful Accounts	(15)	(17)
Total	616	748
Other Current Assets
Commodity Derivative Assets	180	0
Inventories, Materials and Supplies	55	66
Inventories, Crude Oil	12	16
Assets Held for Sale	133	629
Restricted Cash	3	38	$ 30
Prepaid Expenses and Other Assets, Current	35	31
Total	418	780
Other Noncurrent Assets
Equity Method Investments	286	305
Customer-Related Intangible Assets, Net	310	0
Mutual Fund Investments	38	57
Net Deferred Income Tax Asset	21	25
Other Assets, Noncurrent	76	74
Total	731	461
Other Current Liabilities
Production and Ad Valorem Taxes	103	84
Commodity Derivative Liabilities	1	58
Income Taxes Payable	22	18
Asset Retirement Obligations	118	51
Interest Payable	66	67
Current Portion of Capital Lease Obligations	41	61
Liabilities Associated with Assets Held for Sale	1	55
Compensation and Benefits Payable	83	98
Other Liabilities, Current	84	86
Total	519	578
Other Noncurrent Liabilities
Deferred Compensation Liabilities	147	197
Asset Retirement Obligations	762	824
Marcellus Shale Exit Cost Accrual	67	76
Production and Ad Valorem Taxes	83	69
Commodity Derivative Liabilities	26	15
Other Liabilities, Noncurrent	80	64
Total	$ 1,165	$ 1,245
Tamar and Dalit Fields
Other Noncurrent Liabilities
Ownership interest	7.50%